Telling the Evolutionary Time: Molecular Clocks and the Fossil Record

Table 6.1

Heterogeneity of rates of substitution in pairs of phylogenetically related genera and species

a Number of substitutions per site between the two sequences out

of 620 sites, after correction for multiple hits according to K

imura’s two-parameter

model.b Pairwise-distance rate (in

substitutions/1000 sites per 10

6 years) calculated as PDR=K/2T (Li and Graur1991).

c Individual lineage rates (in substitutions/1000 sites per 10

6 years) of the first, respectively the second taxonof the pair, calculated directly on maximum

likelihood tree reconstructions by attributing divergence times to

either terminal or terminal and internal branch lengths(as p

roposed by Hillis

et al.

1996).

EVOLUTION IN THE STEM-LINEAGE OF FORAMINIFERA 113